One of the goals of the NEI is to support researchers on the quest to prevent and treat eye blinding diseases such as Age-related Macular Degeneration (AMD), retinitis pigmentosa and diabetic retinopathy. We have established a retina regeneration model where we can easily manipulate key molecular pathways that could control retina repair and regeneration. The embryonic chick has the ability to regenerate its retina upon injury/removal from a population of retinal stem/progenitor cells located in the ciliary margin of the eye or via the transdifferentiation of retinal pigmented epithelium (RPE) with the aid of fibroblast growth factor (FGF). We have determined that the hedgehog (Hh) pathway can modulate these regenerative abilities interacting with the FGF pathway to either induce or inhibit regeneration depending on the mode of activation. In this proposal, we would like to delineate the signaling pathways involved in both types of regeneration and elucidate key molecules that regulate these processes. Studies in Aim 1 will determine the expression pattern of molecules involved in the FGF and Hh signaling pathways during retina development and regeneration in the embryonic chick eye via in situ hybridization, qRTPCR, immunohistochemistry and Western blotting to further define the mechanisms involved in both modes of regeneration. Aim 2 will determine how cell cycle molecules are regulated by the FGF and Hh pathways and how Hh stimulates regeneration from the ciliary margin. Aim 3 will determine how FGF induces transdifferentiation at embryonic day 4 (E4) but not at embryonic day 5 (E5) and how Hh signaling negatively regulates this process at E4. The regulation of cell cycle molecules by FGF and Hh in the RPE of retinectomized eyes will also be addressed. For these last two aims, in vivo and in vitro experiments have been designed to test for inhibition and over activation of molecules/pathways and a series of diagnostic assays will be used. Aim 4 will provide a global view of gene regulatory networks and pathways that are involved in retina regeneration via microarray analysis. The leading causes of vision impairment and blindness in the United States are primarily age related eye diseases including Age-related Macular Degeneration. No effective treatment has been developed to replace the lost retina cells in these diseases. This study will pinpoint molecules involved in the replacement of retina cells and could shed light into future treatments.